Not necessarily that unusual. The European ancestors of Mexicans were mostly Spaniards, many of whom had Sephardic Jewish and/or Moorish (North African Berbers/Middle Eastern Arabs) ancestry in addition to the native Iberian, Celtic, Basque, Roman, Visigothic, and other genetic influences present in Spain.

It's also my understanding that most of the Spaniards who settled in colonial New Spain (which later became Mexico) were from the southernmost regions of Spain like Andalusia, where Moorish and Jewish influence was strongest, including in the genetic composition of the population. The Spanish dialects of Latin America are mostly derived from Andalusian dialects of Castilian Spanish according to most scholarly research.

Another possible explanation for a higher Middle Eastern DNA result in your grandfather may also be due to entirely different reasons though, such as perhaps more recent immigrant ancestors from the Middle East who settled in Mexico. It's said that quite a few Syrians, Lebanese, and Palestinians immigrated to Mexico. Two famous examples of their descendants are Salma Hayek and Carlos Slim. Maybe your grandfather has some Syrian/Lebanese ancestry.

Also, your grandfather is still over 25% Native American, which of course is very typical for Mexicans, although I'd imagine that the average Mexican has a higher Native American DNA percentage, as in more along the lines of 40-60% Native American, but there's variation across Mexico by region and family of course. Northern Mexicans generally have more European/Spanish ancestry than Mexicans in the central and southern regions, who conversely have a lot more Native American ancestry on average. Light-skinned and more European-looking "mestizos' (people of mixed Spaniard/Indian ancestry) are more commonly found in these northern regions of Mexico.